The present invention concerns a lighting device for an operational field of the type without any cast shadow, particularly but not exclusively limited to the dental surgery field, including a lighting head fed with light by cords of optical fibres directing the light produced by a light generator.
There already exist lighting devices for limiting cast shadows. The devices most currently used in the medical or dental field are shadowless lamps(copyright) comprising a lighting head having a glass parabolic reflector associated with one or several lamps or sets of mirrors.
One of the drawbacks of shadowless lamps(copyright) is that their light source is located at the level of the lighting head and produces a quantity of heat in a work zone prejudicial for practicians and patients.
Another drawback of this type of lighting is its significant volume rendering it relatively bulky.
Systems have already been put forward for lighting a targeted zone fed by optical fibre and an off-set light source for limiting the heat given off at the level of the operational field. For example, in this respect one could cite the lighting device described in the patent FR 1 431 405. However, this device retains a relatively significant volume.
Moreover, it is unable to fully satisfy the need of localised lighting, especially in the dental field, namely obtaining a luminous zone, not circular but having an approximately rectangular shape.
The object of the present invention is to have a product able to obtain these performances whilst also reducing the amount of heat in the work zone.
In accordance with the invention, this result is obtained with a lighting device for an operational field of the cast shadow type, particularly by not exclusively limited for dental surgery, including a lighting head fed with light by at least one of the cords of optical fibres directing the light produced by a light generator placed at a certain distance from the lighting head, characterised in that the light generator comprises a mechanical system for moving away or bringing closer a start end piece of the cords with respect to a light generator lamp.
In addition, the lighting head comprises means to project onto the work zone an approximately rectangular light spot required for illuminating the operational field.
According to one variant, the lighting head comprises:
at the frontal portion, at least two rear flat face aspheric lenses arranged on both sides of the longitudinal axis of the lighting head and having an angular positioning a with respect to the longitudinal axis allowing convergence of the light issued at the outlet by the two lenses,
an optical fibre cord end directed perpendicular to the rear flat face of each aspheric lens, the optical fibres having at the fibre outlet at the level of the end an oblong-shaped section.
The angular positioning xcex1 with respect to the longitudinal axis is preferably about 5.5xc2x0 and the distance between the frontal portion of the end and the flat rear face of each aspheric lens is about 35 mm.
Thus, the device of the invention is able to obtain a rectangular light spot with dimensions of 10xc3x9720 to 70 cm of the lighting head.
According to a second variant, the lighting head comprises a concave reflector receiving the light from an outlet end piece of an optical fibre cord and sending it towards the operational field.
The invention shall be more readily understood from a reading of the following description with reference to the accompanying drawings on which
FIG. 1 is a skeleton diagram of a lighting system according to a first variant,
FIG. 2 is a cutaway bottom view of a lighting head according to a first variant,
FIG. 3 is a front view of the lighting head of FIG. 2,
FIG. 4 is a diagrammatic of the top of the light generator,
FIGS. 5a and 5b are respectively cutaway side and front views of a cord end of optical fibres,
FIG. 6 is a cutaway top view of a lighting head according to a second variant,
FIG. 7 is a perspective view of the light outlet and the reflector of the variant of FIG. 6.